Calprotectin (S100A8/S100A9) and Myeloperoxidase: Co-Regulators of Formation of Reactive Oxygen Species

Inflammatory mediators trigger polymorphonuclear neutrophils (PMN) to produce reactive oxygen species (ROS: O2-, H2O2, ∙OH). Mediated by myeloperoxidase in PMN, HOCl is formed, detectable in a chemiluminescence (CL) assay. We have shown that the abundant cytosolic PMN protein calprotectin (S100A8/A9) similarly elicits CL in response to H2O2 in a cell-free system. Myeloperoxidase and calprotectin worked synergistically. Calprotectin-induced CL increased, whereas myeloperoxidase-triggered CL decreased with pH > 7.5. Myeloperoxidase needed NaCl for CL, calprotectin did not. 4-hydroxybenzoic acid, binding ∙OH, almost abrogated calprotectin CL, but moderately increased myeloperoxidase activity. The combination of native calprotectin, or recombinant S100A8/A9 proteins, with NaOCl markedly enhanced CL. NaOCl may be the synergistic link between myeloperoxidase and calprotectin. Surprisingly- and unexplained- at higher concentration of S100A9 the stimulation vanished, suggesting a switch from pro-oxidant to anti-oxidant function. We propose that the ∙OH is predominant in ROS production by calprotectin, a function not described before

Incidence de l'expérience de l'opérateur sur la pose de la digue dentaire : évaluation prélimaire sur simulateur

The dental dam placement is a mandatory prerequisite before any endodontic treatment. Nevertheless, international prevalence studies reveal that its use remains limited. One of the main reasons given by the practitioners is the time required to its placement. Therefore, this work has been performed to evaluate the influence of the operator experience on the rubber dam placement time, on dental simulator. In the first part, we will describe the dental dam and the main advantages of its use in conservative dentistry and endodontics. Prevalence studies conducted on the dental dam set up in different countries will be also presented in this part. The second part will present the implementation of the experimental study, the material used and the group constitution. The results of this preliminary study will be presented in a third part before being discussed.La mise en place de la digue dentaire est un prérequis obligatoire lors de tout traitement endodontique. Cependant, les études de prévalence, au niveau international, révèlent que son utilisation reste limitée. Une des principales raisons évoquées par les praticiens est le temps nécessaire à sa pose. C’est pourquoi, ce travail a été réalisé afin d’évaluer l’influence de l’expérience de l’opérateur sur le temps de pose de la digue dentaire sur simulateur. La première partie consiste en la présentation de généralités sur la digue dentaire et les avantages majeurs procurés par son utilisation en odontologie conservatrice et endodontie. Les principales études de prévalence menées dans différent pays sur la pose de la digue dentaire seront également présentées dans cette partie. Dans un second temps, nous décrirons la mise en œuvre de l’étude menée, le matériel utilisé ainsi que la constitution des groupes d’études. La troisième partie présentera les résultats obtenus dans cette étude préliminaire et ces deniers seront discutés

A study of direct photon production in proton-proton and antiproton-proton interactions at square root of s = 24.3 GeV.

Results from the data taken by the UA6 experiment in 1988 and 1989 are presented. UA6 was a fixed target experiment utilizing a hydrogen jet target installed in the tunnel of the Super Proton Synchrotron (SPS) at CERN, Geneva. Switzerland. The experiment took data during collider operation, when the accelerator collided beams of protons and antiprotons. By rotating the esperiment, data could be taken for both pp and pp interactions. This made UA6 unique in its ability to observe pp interactions at fixed target energies and compare them to data from pp interactions recorded by the same apparatus. The results described in this dissertation are the measurement and comparison of direct photon production at high transverse momentum (4.1 to 6.1 GeV) in both pp and pp collisions. The difference between the cross sections for these two interactions provides a means of extracting the Quantum Chromodynamic (QCD) scale parameter, $\Lambda{(4)\over MS}$. In addition, both cross sections depend on the gluon distribution in the proton in leading order QCD, making them a sensitive means of investigating this distribution. Results on $\Lambda{(4)\over MS}$ and the gluon distribution are presented after a detailed description of the UA6 apparatus, data preparation and analysis, and the cross section measurements.Ph.D.PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103776/1/9409713.pdfDescription of 9409713.pdf : Restricted to UM users only